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1.
Based on this preliminary study, a metric ton of dry southern red oak chips subjected to a first-stage dilute sulfuric acid
hydrolysis would yield 132 kg of xylose and 40 kg of glucose and mannose. A second-stage dilute sulfuric acid hydrolysis on
the first-stage residue would yield only 128 kg of additional glucose, but a second-stage cellulytic enzyme hydrolysis on
the first-stage residue would yield an additional 265 kg of glucose. Fermentation of these hydrolyzates would show that the
hybrid process would yield over 50% more ethanol. Results on other biomass are also included. 相似文献
2.
Nonisothermal simultaneous saccharification and fermentation for direct conversion of lignocellulosic biomass to ethanol 总被引:1,自引:0,他引:1
The enzymatic reaction in the simultaneous saccharification and fermentation (SSF) is operated at a temperature much lower
than its optimum level. This forces the enzyme activity to be far below its potential, consequently raising the enzyme requirement.
To alleviate this problem, a nonisothermal simultaneous saccharification and fermentation process (NSSF) was investigated.
The NSSF is devised so that saccharification and fermentation occur simultaneously, yet in two separate reactors that are
maintained at different temperatures. Lignocellulosic biomass is retained inside a column reactor and hydrolyzed at the optimum
temperature for the enzymatic reaction (50°C). The effluent from the column reactor is recirculated through a fermenter, which
runs at its optimum temperature (20-30°C). The cellulase enzyme activity is increased by a factor of 2-3 when the hydrolysis
temperature is raised from 30 to 50°C. The NSSF process has improved the enzymatic reaction in the SSF to the extent that
it reduces the overall enzyme requirement by 30-40%. The effect of temperature on β-glucosidase activity was the most significant
among the individual cellulase compounds. Both ethanol yield and productivity in the NSSF are substantially higher than those
in the SSF at the enzyme loading of 5 IFPU/g glucan. With 10 IFPU/g glucan, improvement in productivity was more discernible
for the NSSF. The terminal yield attainable in 4 d with the SSF was reachable in 40 h with the NSSF. 相似文献
3.
Chen Chee-Shan Chan E. Wang S. L. Gong C. S. Chen L. F. 《Applied biochemistry and biotechnology》1994,(1):531-544
A self-aggregating strain ofSaccharomyces uvarum (U4) was used as a biocatalyst to carry out continuous ethanol fermentation in a tower fermentor equipped with a cell separator.
Cell aggregates (2–3 mm) formed a stable packed bed in the fermentor, and the cell separator retained yeast cells effectively.
Corn steep liquor was used as a nitrogen source for the fermentation of corn syrup and black strap molasses. An ethanol productivity
of 54 g/L/h was reached using corn syrup at a dilution rate of 0.7/h, and sugar concentration in the feed was 15% (w/v). For
molasses fermentation, an ethanol productivity of 22 g/L/h was obtained at a dilution rate of 0.7/h, and sugar concentration
in the feed was 12.5% (w/v). Ethanol yields obtained from tower fermentation are higher than those obtained from flask fermentation
(96% for corn syrup fermentation and 92% for molasses fermentation). No significant loss in fermentation activity was observed
after 3 mo of operation. 相似文献
4.
Chiang Heien-Kun Foutch Gary L. Fish Wayne W. 《Applied biochemistry and biotechnology》1991,(1):513-525
Acetaldehyde has been produced biologically using whole-cellPichia pastoris in a semibatch fermentor. Ethanol and air were fed continuously, and the product, acetaldehyde, was removed by the air stream.
Operation of the reactor exceeded 100 h, maintaining high alcohol oxidase activity. Low cell-mass concentration (9.9 g/L)
minimized product inhibition. Ethanol concentration in the broth, oxygen concentration in the air, and pH were evaluated for
their effects on the fermentation process. 相似文献
5.
Experimental results are presented for continuous conversion of pretreated hardwood flour to ethanol. A simultaneous saccharification
and fermentation (SSF) system comprised ofTrichoderma reesei cellulase supplemented with additional β-glucosidase and fermentation bySaccharomyces cerevisiae was used for most experiments, with data also presented for a direct microbial conversion (DMC) system comprised ofClostridium thermocellum. Using a batch SSF system, dilute acid pretreatment of mixed hardwood at short residence time(10 s, 220°C, 1% H2SO4) was compared to poplar wood pretreated at longer residence time (20 min, 160°C, 0.45% H2SO4). The short residence time pretreatment resulted in a somewhat (10–20%) more reactive substrate, with the reactivity difference
particularly notable at low enzyme loadings and/or low agitation. Based on a preliminary screening, inhibition of SSF by byproducts
of short residence time pretreatment was measurable, but minor. Both SSF and DMC were carried out successfully in well-mixed
continuous systems, with steady-state data obtained at residence times of 0.58–3 d for SSF as well as 0.5 and 0.75 d for DMC.
The SSF system achieved substrate conversions varying from 31% at a 0.58-d residence time to 86% at a 2-d residence time.
At comparable substrate concentrations (4–5 g/l) and residence times (0.5–0.58 d), substrate conversion in the DMC system
(77%) was significantly higher than that in the SSF system (31%). Our results suggest that the substrate conversion in SSF
carried out in CSTR is relatively insensitive to enzyme loading in the range 7–25 U/g cellulose and to substrate concentration
in the range of 5–60 g/L cellulose in the feed. 相似文献
6.
Srivastava Vipul J. Biljetina Richard Isaacson H. Ronald Hayes Thomas D. 《Applied biochemistry and biotechnology》1989,(1):587-602
Applied Biochemistry and Biotechnology - The Institute of Gas Technology has developed a novel, solids-concentrating (SOLCON®) bioreactor to convert a variety of individual or mixed feedstocks... 相似文献
7.
Sun May Y. Nghiem Nhuan P. Davison Brian H. Webb Oren F. Bienkowski Paul R. 《Applied biochemistry and biotechnology》1998,(1):429-439
The production of ethanol from starch was studied in a fluidized-bed reactor (FBR) using co-immobilizedZymomonas mobilis and glucoamylase. The FBR was a glass column of 2.54 cm in diameter and 120 cm in length. TheZ. mobilis and glucoamylase were co-immobilized within small uniform beads (1.2-2.5 mm diameter) of κ-carrageenan. The substrate for
ethanol production was a soluble starch. Light steep water was used as the complex nutrient source. The experiments were performed
at 35κC and pH range of 4.0-5.5. The substrate concentrations ranged from 40 to 185 g/L, and the feed rates from 10 to 37
mL/min. Under relaxed sterility conditions, the FBR was successfully operated for a period of 22 d, during which no contamination
or structural failure of the biocatalyst beads was observed. Volumetric productivity as high as 38 g ethanol/(Lh), which was
74% of the maximum expected value, was obtained. Typical ethanol volumetric productivity was in the range of 15-20 g/(Lh).
The average yield was 0.49 g ethanol/g substrate consumed, which was 90% of the theoretical yield. Very low levels of glucose
were observed in the reactor, indicating that starch hydrolysis was the rate-limiting step. 相似文献
8.
Ballesteros I. Oliva J. M. Carrasco J. Cabañas A. Navarro A. A. Ballesteros M. 《Applied biochemistry and biotechnology》1998,(1):369-381
In this work, the effect of the addition of different concentrations of Tween-80 and three different zeolite-like products
on enzymatic hydrolysis, ethanol fermentation, and simultaneous saccharification and fermentation (SSF) process has been investigated.
The ability of these products to enhance the effectiveness of the SSF process to ethanol of steam-exploded poplar biomass
using the thermotolerant strainKluyveromyces marxianus EMS-26 has been tested.
Tween-80 (0.4 g/L) increased enzymatic hydrolysis yield by 20% when compared to results obtained in hydrolysis in absence
of the additive. Zeolite-like products (ZESEP-56 and ZECER-56) (2.5 g/L) improved rates of conversion and ethanol yields in
the fermentation of liquid fraction recovered from steam-exploded poplar. The periods required for the completion of fermentation
were approx 10 h in the presence of zeolite-like products and 24 h in the absence of additives. The probable mode of action
is through lowered levels of inhibitory substances because of adsorption by the additive. 相似文献
9.
The effect of the trace metals Cu, K, Na, and Ca, separately or in mixture, on fermentation time, ethanol production rate,
and cell growth in the fermentation of synthetic media containing sucrose is discussed. The results are related to the range
of contents found in raw materials, molasses and raisins, in order to determine their optimum concentrations for alcohol production. 相似文献
10.
Studies have been carried out using immobilized Z.mobilis in fluidized-bed bioreactors and have emphasized operation during high productivity and conversion. The bacteria are immobilized
within small uniform beads (~1 to 1.5-mm diam) of K-carrageenan at cell loadings of 15-50 g (dry wt)/L. Conversion and productivity
were measured under a variety of conditions, including feedstocks, flow rates, temperature, pH, and column sizes (up to 2.5
m tall). Volumetric productivities of 50-120 g EtOH/h-L reactor volume have been achieved. Productivities of 60 g/h-L are
demonstrated from a 15% feed with residual glucose concentrations of less than 0.1% and 7.4% EtOH in the tallest fermentor.
Among feeds of 10, 15, and 20% dextrose, the 15% gave the highest productivity and avoided substrate inhibition. A temperature
of 30°C and pH 5 were the optimum conditions. The ethanol yield was shown to be nearly constant at 0.49 g EtOH/g glucose,
or 97% of the theoretical under a variety of conditions and transients. The biocatalyst beads have been shown to remain active
for two months. Nonsterile feed has been used for weeks without detrimental contamination. The advantages of this advanced
bioreactor system over conventional batch technology are discussed. 相似文献
11.
Freire Denise M. Teles Elaine M. F. Bon Elba P. S. Anna Geraldo Lippel Sant’ 《Applied biochemistry and biotechnology》1997,(1):409-421
A preliminary screening work selectedPenicillium restrictum as a promising micro-organism for lipase production. The physiological response of the fungus towards cell growth and enzyme
production upon variable carbon and nitrogen nutrition, specific air flow rate (Qa) and agitation (N) was evaluated in a 5-L
bench-scale fermenter. In optimized conditions for lipase production meat peptone at 2% (w/v) and olive oil at 1% (w/v) were
used in a growth medium with a C/N ratio of 9.9. Higher C/N ratios favored cell growth in detriment of enzyme production.
Low extracellular lipase activities were observed using glucose as carbon source suggesting glucose regulation. Final lipase
accumulation of 13,000 U/L was obtained, using optimized specific air flow rate (Qa) of 0.5 wm and an impeller speed (N) of
200 rpm. Agitation showed to be an important parameter to ensure nutrient availability in a growth medium having olive oil
as carbon source. 相似文献
12.
Cao Ning-Jun Xu Qin Chen Chee-Shan Gong C. S. Chen L. F. 《Applied biochemistry and biotechnology》1994,(1):521-530
Cellulose gel with < 10% of crystallinity was prepared by treatment of microcrystalline cellulose, Avicel, with zinc chloride
solution at a ratio of zinc chloride to cellulose from 1.5 to 18 (w/w). The presence of zinc ions in the cellulose gels enhanced
the rate of hydrolysis and glucose yield. The evidence obtained from X-ray diffraction, iodine absorption experiments; and
Nuclear Magnetic Resonance spectra analysis suggested the presence of zinc-cellulose complex after Avicel was treated with
zinc chloride. Zinc-cellulose complex was more susceptible to hydrolysis than amorphous cellulose. Under the experimental
condition, cellulose gels with zinc ions were hyrolyzed to glucose with 95% theoretical yield and a concentration of 14% (w/v)
by cellulases within 20 h. The same gel was hydrolyzed by acid to glucose with 91.5% yield and a concentration of 13.4% (w/v). 相似文献
13.
Ballesteros I. Ballesteros M. CabaÑas A. Carrasco J. MartÍn C. Negro M. J. Saez F. Saez R. 《Applied biochemistry and biotechnology》1991,(1):307-315
A total of 27 yeast strains belonging to the groupsCandida, Saccharomyces, andKluyveromyces were screened for their ability to grow and ferment glucose at temperatures ranging 32-45°C.
K. marxianus andK. fragilis were found to be the best ethanol producing organisms at the higher temperature tested and, so, were selected for subsequent
simultaneous saccharification and fermentation (SSF) studies. 相似文献
14.
A thermochemical pretreatment of bagasse for the enzymatic hydrolysis has been carried out, in which pretreatment bagasse
was autoclaved with binary solvent, composed of Water and organic solvent having upper critical temperature (UCT) on the mutual
solubility curve. The pretreatment was named “UCT-solvent pretreatment.” The hydrophobic decomposition products from lignin
and hemicellulose, that dissolved in organic phase at room temperature, could be easily separated from the solid and sugars
in the aqueous phase. By using UCT-solvent instead of only water, the sugar recoveries from bagasse through the pretreatment
and the enzymatic hydrolysis were much improved. There exists an optimal mixing ratio between organic solvent and water to
maximize the effect of the pretreatment for enzymatic hydrolysis. The optimal ratio can be explained by the competitive effect
between the ability of water as a reagent for the hydrolysis and the ability of solvent for the extraction of the decomposition
product, and furthermore by the competitive effect between affinities of the solvent to hydrophilic hemicellulose and hydrophobic
lignin. Decomposition of hemicellulose at lower temperature than 190°C was decreased, and hence the degradation of xylose
during the pretreatment decreased. These favorable effects of UCT-solvent pretreatment are significantly attributed to the
formation of the homogeneous single phase of organic solvent and water at high temperature and the phase separation at room
temperature. 相似文献
15.
16.
Stenberg Kerstin Tengborg Charlotte Galbe Mats Zacchi Guido Palmqvist Eva Hahn-Hägerdal Bärbel 《Applied biochemistry and biotechnology》1998,(1):697-708
In ethanol production from lignocellulose by enzymatic hydrolysis and fermentation, it is desirable to minimize addition of
fresh-water and waste-water streams, which leads to an accumulation of substances in the process. This study shows that the
amount of fresh water used and the amount of waste water thereby produced in the production of fuel ethanol from softwood,
can be reduced to a large extent by recycling of either the stillage stream or part of the liquid stream from the fermenter.
A reduction in fresh-water demand of more than 50%, from 3 kg/kg dry raw material to 1.5 kg/kg dry raw material was obtained
without any negative effects on either hydrolysis or fermentation. A further decrease in the amount of fresh water, to one-fourth
of what was used without recycling of process streams, resulted in a considerable decrease in the ethanol productivity and
a slight decrease in the ethanol yield 相似文献
17.
18.
Donnelly Mark I. Millard Cynthia Sanville Clark David P. Chen Michael J. Rathke Jerome W. 《Applied biochemistry and biotechnology》1998,(1):187-198
Escherichia coli strain NZN111, which is unable to grow fermentatively because of insertional inactivation of the genes encoding pyruvate:
formate lyase and the fermentative lactate dehydrogenase, gave rise spontaneously to a chromosomal mutation that restored
its ability to ferment glucose. The mutant strain, named AFP111, fermented glucose more slowly than did its wild-type ancestor,
strain W1485, and generated a very different spectrum of products. AFP111 produced succinic acid, acetic acid, and ethanol
in proportions of approx 2:1:1. Calculations of carbon and electron balances accounted fully for the observed products; 1
mol of glucose was converted to 1 mol of succinic acid and 0.5 mol each of acetic acid and ethanol. The data support the emergence
in E.coli of a novel succinic acid:acetic acid:ethanol fermentation pathway. 相似文献
19.
Phillips J. R. Klasson K. T. Clausen E. C. Gaddy J. L. 《Applied biochemistry and biotechnology》1993,(1):559-571
The anaerobic bacteriaClostridium ljungdahlii produces ethanol and acetate from CO, CO2, and H2 in synthesis gas. Early studies with the bacterium showed that relatively high concentrations of ethanol could be produced
by lowering the fermentation pH and eliminating yeast extract from the medium in favor of a defined medium. This article presents
the results from a medium development study based on the aerobic bacteriumEscherichia coli. The results of continuous-reactor studies in a continuously stirred tank reactor (CSTR) with and without cell recycle are
shown to demonstrate the utility of this improved medium. 相似文献
20.
The potential market for lactic acid as the feedstock for biodegradable polymers, oxygenated chemicals, and specialty chemicals
is significant. L-lactic acid is often the desired enantiomer for such applications. However, stereospecific lactobacilli
do not metabolize starch efficiently. In this work, Argonne researchers have developed a process to convert starchy feedstocks
into L-lactic acid. The processing steps include starch recovery, continuous liquefaction, and simultaneous saccharification
and fermentation. Over 100 g/L of lactic acid was produced in less than 48 h. The optical purity of the product was greater
than 95%. This process has potential economical advantages over the conventional process. 相似文献